In communication systems, radar, direction finding and other broadband multifunction systems having limited aperture space, it is often desirable to couple a radio frequency receiver and/or transmitter to an array of antenna elements. It is also desirable that such an array have dual polarized antenna elements, which are capable of achieving significant performance advantages over single polarization antenna arrays. The dual polarization antenna is particularly useful with energy waves such as those employed in the radio frequency spectrum having two orthogonal components which are orthogonally polarized with respect to each other. The orthogonal polarization of the energy waves allows for the possibility of broadcasting two different signals at the same operating frequency, thereby doubling the information sent at the same frequency by using two separate antennas. In doing so, one signal is derived from the principle polarized antenna element and the second signal is derived from the orthogonal polarized antenna element.
One such type of dual polarized antenna array is known as a notch-antenna. A notch-antenna array is an antenna array that radiates and/or collects RF energy through an array of notches or slots. Notch-antennas typically exhibit wide beam with broad bandwidth characteristics, advanced beam-forming compatibility, and a low radar cross-section compatibility.
To manufacture such an array, separate semi-rigid coaxial cables are fed through a channel in each antenna and bonded into place with an electrically conductive adhesive. Accurate and uniform placement of these cables to ensure proper electrical contact is tedious and is often performed with minimal or obscured visibility. Moreover, the viscosities of the conductive adhesives/epoxies used to bond the cables in place varies as the adhesives begin to cure. Inconsistencies of the adhesive viscosity leads to varying amounts of adhesive being applied throughout the manufacturing process, which leads to non-uniform antenna element-to-element electrical radiation performance usually resulting in inconsistent voltage standing wave ratios (VSWR). As VSWR increases, efficiency of the antenna radiator decreases. Non-uniformity of the elements also leads to other performance issues including higher radiation pattern sidelobes, higher mutual coupling, and higher backscatter adding to radiation performance differences throughout the field of view of the desired radiation pattern.
These manufacturing and performance issues are typically experienced for radiator antenna elements operating at higher frequencies such as above 300 MHz where the antenna element size is physically smaller. At millimeter wave frequencies above 20 GHz, where wavelengths are less than six tenths of an inch, these manufacturing and performance issues are pronounced.
In general, multiple antenna radiators are assembled in an egg crate or honeycomb type of array structure. This type of array structure has substantial drawbacks. To ensure intimate electrical connection between adjacent radiating elements, conventional manufacturing techniques require electrically conductive fillets at the joints between adjacent radiator elements. However, applying these fillets after the antenna radiators are assembled into the planar array orientation is difficult as physical obstruction prevents proper application of the adhesive. For higher frequency arrays, such as at millimeter-wave frequencies, the physical obstruction is exacerbated.
While such fabrication may be feasible when making a small number of large-sized (low frequency) antenna arrays, it quickly becomes unfeasible when making large arrays of dozens of small high frequency antenna radiators.
In light of the above drawbacks, existing notch-antennas are difficult, time-consuming, and expensive to manufacture. Therefore, it would be highly desirable to have a notch-antenna array that addresses the above described drawbacks by minimizing the number of components in the assembly, simplifying the assembly process, and reducing the cost of manufacture.